This invention relates to new nematic liquid-crystal substances for electro-optical components for the modulation of incident or traversing light as well as for the representation of numerals, signs and images as well as to processes for their manufacture.
Electro-optical components on the basis of twisted layers (Schedt-Helfrich cells) or on the basis of guest-host effects require nematic liquid crystals with a high positive dielectric anisotropy, low melting and high clear temperatures. Depending on the activation variant, certain values of optical anisotropy, of electro-optical characteristics and of viscosity constants are required, as well as elastic constants. There is no pure substance which fulfills all requirements. For this reason without exception, mixtures whose composition is adjusted to the particular requirements of each situation also employed. To vary the qualities of these mixtures, a conceivably wide range of different substances is needed, possibly from different classes of substances, in order to leave enought latitude for a change in characteristics of the mixtures of substances. For this reason, there is an ongoing search for new liquid crystals with favorable qualities.
The prior art merely describes unsubstituted decalin carbonic acids. The nonmesogeneous cis-decalin-2-carbonic acid is generated as the principal product through the hydrogenation of naphthalin-2-carbonic acid with platinum dioxide in glacial crystalline acetic acid at 240 at, (W. Dauben, E. Hoerger, J. Amer. Chem. Soc. 73, 1504 (1951)). All hydrogenation tests conducted with Raney-nickel in an alkaline medium under high pressure led to 5,6,7,8-tetrahydronaphthalene-2-carbonic acid (G. Stork, J. Amer. Chem. Soc. 69, 576 (1947)). It was only possible to synthesize the trans-decalin-2-carbonic acid from trans-decalin through chlorination and subsequent Grignard reaction, which produced a low yield (1. N. B. Chapman, J. Shorter, K. J. Toine, J. Chem. Soc. 1964, 1077. 2. W. Dauben, R. Tweit, J. Amer. Chem. Soc. 76, 3197 (1954)).
The object of the invention is to create substances for electro-optical components which combine chemical and thermal stability with low melting and high clear points at low operating voltage, as well as to the processes for their preparation.